Control device



1939. N. c. SCHELLENGER 7, 3

CONTROL DEVICE Filed Dec. 14, 1955 3 Sheets-Sheet l INVENTOR.

NE WTON 6. SCHELLENGER.

Oct. 24, 1939. N Q SCHELLENGER 2,177,283

CONTROL DEVICE Filed Dec. 14, 1935 3 Sheets-Sheet 2 [NI/EN TOR. NEWTON 6.? SCHELLENGER ATTX Oct. 24, 1939. c SCHELLENGER 2,177,283

CONTROL DEVICE Filed Dec. l4 1935 3 Sheets-Sheet 5 DIRECTION OF JNVENTOR.

Mwzwv 67 Sc/{15 LEA/GER,

Patented Oct. 24, 1939 UNITED STATES PATENT OFFICE CONTROL DEVICE Application December 14, 1935, Serial No. 54,407

This invention relates to a new and improved switch and shield construction and more particularly to devices of this character adapted for use in association with variable resistance controls.

In connection with radio receiving sets and also in connection with sound amplifiers for use in radio reception and transmission and in public address systems, it has become customary to use a circuit controlling switch in connection with a variable resistance. The switch and variable resistance may be in the same or different circuits but they are jointly operated by means of a single shaft, the switch being operated at a predetermined point in relation to the control of the variable resistance.

In many such circuits, especially where a low voltage circuit is controlled by the switch as in automobile radios or other such units operated from batteries, a relatively small increase in the resistance in the circuit will have serious effects upon theoperation of the apparatus. When used in connection with high voltage circuits the current carried by the switch or variations in that current due to any cause may have an effect upon the adjacently placed variable resistances. These variable resistances are commonly located in portions of the circuits which are highly sensitive so that they are afiected by the adjacent switch circuit in a manner to seriously modify the resultant sound reproduction of the circuit.

With associated switch and variable resistance devices which are jointly operated, it is essential that the switch be definitely and-accurately 1ocated in relation to the resistance and to the actuating mechanism. It is important that the switch have a substantially constant contact resistance throughout an extended operating life, both because of the effect a variable switch re sistance will have on the switch circuit and because of undesirable effects a poor switchcontact may have upon the adjacent variable resistance. The design of the switch contacts thereforie should be such as to minimize arcing with result- 15 ant pitting and wear of the contact surfaces and preferably to cause the arcing to occur upon other the conducting portions cf the contact surit has been customary to mount the variable resistance upon a fiat base member carrying the contact cperating member. It has also been cu..- tornary to support the switch mechanism directly or indirectly from a housing secured to the base member. These housings have tubular side walls usually formed of metal by a drawing operation.

9 Claims. (01. 201-35) They are usually formed from a flat blank and it is customary to lay out the blank with extending lugs which, after the drawing operation, form securing lugs at the free edge of the tubular side wall for use in securing the housing to the vari- 5 able resistance base member. It has been found in practice that with common types of sheet metal there is a material variation in the drift of these lugs during the drawing operation so that the lugs are not uniformly spaced in the finished 10 housings. This makes assembly of the housings on the bases diflicult where the lugs fit in notches in the base to locate and secure the housing to the base. It will be apparent, particularly where the housing carries a switch, that it is essential that 18 the housing not only be properly positioned relative to the base, but that it be secured thereto in such manner as to prevent looseness and relative rotary movement of the base and housing.

It is an object of the present invention to pro- 20 vide a new and improved switch mechanism.

It is a further object to provide an electrostatic shield for a switch, so associated with a switch that it functions as a portion of the switch mechanism. a

It is also an additional object 'to provide a new and improved switch and shield assembly adapted for assembly with a variable resistance housing.

It is anadditional object to provide improved switch contact members.

It is a further object to provide a new and improved unit housing and means for assembling the same upon a base.

It is also an object to provide a method of 85 forming an improved housing with accurately positioned securing means.

It is an additional object to provide devices of the character described which are simple in design and construction and adapted for commerclal production.

Other and further objects will appear as the description proceeds.

I have shown "a preferred embodiment of my invention in the accompanying drawings, in which- Figure l is a plan view of the switch in the oil position, and with the actuating parts on dead center;

Figure 2 is a perspective view oi the shield and m stop piate; 4

Figure 3 is a plan view of the switch mechanism with the shield and stop plate in position, the switch and actuating mechanism being in or? position;

nism with a fragmentary showing of the kick-off members carried by the shield;

Figure 7 is an unassembled view of the elements making up the switch actuating mechanism;

Figure 8 is a perspective view of the movable contact and a fixed contact;

Figure 9 is a fragmentary section showing the relation between the fixed and movable contacts when in engagement; 7

Figure 10 is a plan view on an enlarged scale indicating the engagement between the fixed and movable contacts;

Figure 11 is a fragmentary elevation on an enlarged scale showing the method of engagement of the fixed and movable contacts;

Figure 12 is an elevation partly in section showing the switchmechanism and an associated variable resistance mechanism;

Figure 13 is a perspective view of the mounting housing;

Figure 14 is an unassembled perspective view of the housing, switch, variable resistance and grounding plate;

Figure 15 is a. plan view of the under side of the combined switch and variable resistance mechanism;

Figure 16 is a plan view of a sheet metal blank for the housing member; and

Figure 17 is a fragmentary perspective showing the method of locating and connecting the housing and base member.

As best shown in Figure 1, the switch mechanism is mounted on a base plate 2| which may be formed of any suitable non-conducting material, such, for example, as sheet Bakelite or other artificial resin. The base 20 is circular in plan and in the form shown is provided with locating and securing notches 2|, the purpose of which will be discussed hereafter. The fixed contact members 22 and 23 are secured to the base plate 2|) by means of the hollow rivets. and 25. These contact members 22 and 23 are provided with the connecting lug portions 25 and 21 which extend through slots in the base 20 as clearly shown in Figure 4. The body portion of the fixed contact members is held in flat engagement with the face 01 the base 2! and the fit of the securing lug portions 25 and 21 in the openings in the base 20 prevents rotation of the members about their securingrivets 24 and 25. The contacts are thus firmly and positively retained in place. These fixed contact members 22 and 23 are provided with offset portions 28 and 29 respectively, which are provided with angular faces 3| and 3| for engagement by moving contacts. These portions 28 and 29 are raised clear from the base plate 20 an amount suflicient to permit a portion of the movable contact to pass between the base and the fixed contact portion, as will bedescribed hereafter The movable switch arm 32 may also be formed of sheet Bakelite or similar artificial resin or other non-conducting material. The under side of this member is shown in Figure 5 and the member is provided with the opening 32 which fits upon the pivot pin 34. The movable contact 35 comprises a pair of approximately u shaped metallic members 3% and 3'1 as best shown in.

Figure 8, which members are secured to the member 32 by means of the tubular rivets 3B and 33. The member 31 is provided with the downturned fixed contact engaging portions 40 and 4|, while the member 36 is provided with the corresponding upturned fixed contact engaging portions 42 and 43. The thin cover member 44 is similar in shape to the member 32 and overlies that member so as to cover the heads of the movable contact securing rivets 38 and 39 and to thus insulate the movable contact from the switch operating mechanism. This member 44 may be formed of sheet Bakelite or similar material.

The operating cam 45 is U-shaped 'in vertical section, as clearly shown in Figure 7, having upper and lower horizontal legs 48 and 49, joined by a vertical wall 50. The legs 48 and 43 are provided with perforations 5| and 52 to fit on the shank 53 of the pivot pin 34. The upper leg 48 is provided with the notch 54 adapted to receive an actuating pin 55 carried by the disc 58 rotatable with the variable resistance arm, as shown in Figure 12. The lower leg 49 has a T-headed lug 51 extending therefrom, this lug extending through the slot 58 in the head 59 of the pitman 60.

The pitman 60 carries the compression spring 5|, one end of which engages the shoulder 62 on the pitman while the other end engages the abutment member 63. This abutment member 63 is provided with an opening 84 through which the end 65 of the pitman 6B slides. The body of the abutment member 63 extends through corresponding openings in the switch arm cover member 44 and the movable switch arm 32. The tail 6'! of the member 63 fits into aligned notches 68 and 41 formed in the ends of the arm 32 and member 44. This abutment member thus serves jointly with the pivot 34 to hold members 32 and 44 together.

The pivot pin 34 is provided with the enlarged portion 59 below which is the shoulder I0. The perforation 33 in the member 32 and the corresponding perforation in the member 44 fit over the enlarged portion 69, as clearly shown in Figure 12. The enlarged portion II on the pivot pin below the shoulder 10 serves to space the switch mechanism from the base plate 20. As shown in Figure 12, the lower end of the pin 34 is riveted over at 12 toretain the pin in place in the base plate 20. The upper end of the pin 34 is also riveted over at I3 to retain the cam member 48 in place on the pin. The cam member then serves to retain the switch arm and cover member in proper position on the enlarged portion 59.

The shield I4 is provided with three downturned legs 15, I20 and |2I which are provided with the reduced securing lugs I6, I22 and I23. These securing lugs I6, I22 and I23 are of a size to fit in the notches 2| formed in the switch base plate 20 and are so positioned as to register in these notches as shown in Figures 3 and 4. The shield member 14 is also provided with the two downturned stop lugs 11 and I8 adjacent the recess I24 formed in the shield. As shown in Figure 3, these lugs are engaged alternately by the operating cam 45 at its two limits of movement. The lateral extended portions of the switch arm members 32, 44 also alternately engage the inner faces of the legs I20 and I2l at their limits oi movement as shown in Figure 3. The shield "I4 provided with the upstanding lug 19 which serves as a limiting stop for the rotary contact arm of the associated variable resistance. The

center portion of the shield member 14 is formed with the downturned lugs 88 and 8| which in the operation of the switch, as will be hereafter explained, serve to assist in breaking contact between the fixed and movable contact members.

The switch is assembled upon the base 82 of the variable resistance by means of a supporting housing 83 which is preferably formed from sheet metal. This housing 83 is tubular in shape, having an inturned peripheral flange 84 at one end. The flange 84 is provided with inwardly extending portions 85, each of which is provided with a slot 88 adapted to receive one of the securing ears 16, I22 or I23 formed on the shield 14. The portions 15, I28 and I2I of the shield engage the inner surface of the base 28 adjacent the notches 2I through which the ears 16, I22 and I23 pass, and by passing these ears through the perforations 86 and bending them over, the shield and switch base carrying the switch mechanism are mounted in the housing 83. This is clearly shown in the lower portion of Figure 12.

4 As shown in Figure 14 the base 82 of the variable resistance is provided with a pair of notches 81 and 88, which are diametrically opposite each other and equally spaced from the extended ,rportion 89 of the base member, which portioncarries the connecting lugs 98, 9| and 92. These lugs 98, 9| and 92 serve to connect the movable contact and the ends of the variable resistance in the desired circuit. In addition, the base 82 is provided with further notches 93, 94, 95, 96 and 91. The notches 81, 88, 93, 94, 95, 96 and 91 are all positioned to receive corresponding lugs I84, I85, I83, I82, IN, 98 and 99 on the lower edge of the housing 83. The wall of the housing 83 iscut away between the lugs 98 and 99, as shown at I88 in Figures 13 and 14, in order to receive the extended portion 89 of the base member 82. The notches 93 to 91 inclusive, and the coacting lugs 98, 99, I8I, I82 and I83 are so proportioned and located that the lugs will fit into the notches with a slight clearance therein as shown somewhat exaggerated at I21 on Figure 17. The' remaining lugs I84 and I are located at opposite ends of a diameter of the housing and fit into the notches 81 and 88 which are similarly located on the base member 82. These notches and lugs are made of such size that the lugs fit closely in the notches and they serve as a primary locating means to accurately and exactly position the housing upon the base member.

The variable resistance comprises a flat, carbonaceous type of resistor I86, which is secured on the base member 82 by the lugs 98 and 92 in any customary manner. The arm I81 carrying the contact shoe I88 is rotated by means of the shaft I89. The disc 56 is also secured to the shaft I89 by means of a reduced portion IIi of the shaft which is riveted over against a washer II2. This disc carries the pin 55 which serves to engage the notch or fork 54 in the actuating cam 45 as above described. The disc 56 is provided with an arcuate radially extended portion and is provided with upturned extensions II6 which may serve to fasten the assembly to a mounting base or chassis or which may merely extendthrough openings in the mounting member to prevent rotation of the assembly about its axis. In the latter case, the assembly is mounted by nut I25on the bushing H5. The member H4 is also provided with offset extensions II1 which are offset to bear against the outer face of the variable resistance base 82. As best shown in Figure 15, these extensions II1 are engaged by the lugs 98 and 99 formed on the housing member 83. Consequently the member I I4 serves to ground the housing to the bushing II5, which is usually grounded by connection .to a metal chassis or supporting panel.

It will be noted that the body portion of the grounding plate which is located on the opposite side of the resistance base 82 from the resistance strip I86 and aligned with that strip, is spaced from the base 82 as clearly shown in Figures; 12 and 14. This results in materially reducing the capacity coupling between the resistance strip and the grounded plate.

It is believed that the method of assembling the switch elements on. the base plate 28 will be readily understood from the drawings and the description. The base may be blanked out of sheet material, with the various notches and perforations formed at a single operation so that it is comparatively inexpensive to make and much cheaper than molded insulation switch supporting housings which are in general use. The two fixed contacts 22 and23 are inserted and secured in place by their tubular rivets 24 and 25. The pivot member 34 may then be secured in place in the base 28 by riveting over the lower end of the member 34, as shown at 12 in'Flgure 12.

As a separate operation the movable contact assembly 35 is secured to the movable switch arm 32 by means of the rivets 38 and 39; The switch arm 32 may be formed-of sheet insulating material in the same manner as the base 28, being blanked out and perforated in a single operation. After the movable contact assembly 35, comprising members 36 and 31, is secured to the movable arm 32, the abutment member 63 may have its body portion inserted through the slot in the arm and the contact arm cover member 44 is then placed over the contact arm 32, a corresponding perforation fitting over the body 63 of the abutment member. The tail 81 of the abutment member is then forced downwardly to grip the member 44 and fix the members 32 and 44 in assembled relation.

The switch arm, movable contact and abutment assembly may next be placed on the pivot pin 34 resting against the shoulder 18, as best shown in Figure 12. The operating cam 45 may next be placed on pivot pin 53 resting on shoulder 6-9 and the head of the pin riveted there as shown at 13 in Figure 12. The pitman 68 is next secured to the cam 45 by hooking the slot 58 over the T-head 51 of the cam and the spring 6| assembled on the pitman. There are no stops limiting the rotation of the cam 45 on pivot 34 so that the cam and pitman assembly may be swung to one side and the end of the pitman properly in- "serted in the slot 64 in the abutment member 63.

The next step in the assembly is the location of the shield 14 in relation to the base 28 by placing the lugs 16, I22 and I23 in the corresponding notches 2I so that the cut-away portion I24 is located above the cam 45, as best shown in Fig- 15 ure 3.

During this assembly the switch parts are held so that the switch arm members 32 and 44 fit between the legs I20 and I2I of the shield, and the cam 45 fits between the stops TI and I8. Similarly, with the parts positioned in this manner, the pitman 60 and coil spring BI fit between the kick-off members 80 and BI.

The shell or housing 83 is next assembled on the switch assembly, with the lugs I6, I22 and I23 passing through the openings 86 formed. in the extended portions of the flange 84 of the housing. The ears or lugs "I5, I22 and I23 are then bent down firmly against the extended portions 85 and serve to maintain the shield and switch base carrying the switch assembly in proper assembled relation in the housing 33.

The variable resistance assembly shown in Figures 12 and 14 in its specific form is not part of the present invention and its method of assembly need not be described in detail.

When the thimble or bushing H5 is assembled to the base 82, the shield member H4 is also assembled and is held in place by the bushing I I5. I

It must be so assembled in relation to the base that the connecting portions III are located adjacent the notches 86 and 91 in the base. The variable resistance actuating arm and collecting rings are assembled in the usual manner and the assembly held in place by means of the C-washer I30 fitting in agroove I3I in the shaft I09. When the switch assembly carried in the housing is assembled on the variable resistance assembly, it is necessary that the switch mechanism be in proper relationship with the actuating pin 55 so that that pin will properly enter the notch 54 in the cam 45 when the variable resistance is rotated. For example, the parts may be assembled with the switch in the on position and the variable resistance contact member turned well to the limit of clockwise movement. This will insure proper cooperation of the parts after assembly. There is no difficulty in getting the housing and variable resistance base plate in proper registration for assembly since the cutout portion I00 in the housing fits over the extended portion 09 of the base 82.

It will be understood that the lugs 98, 99, IIII, I02 and I03, fit somewhat loosely in their corresponding notches in the base plate so that the accurate assembly of the parts is caused by lugs I04 and I05 which fit very closely in the asso ciated notches in the base plate. When the housing and switch assembly is assembled on the base plate, the lugs 98, 99, Illl, I02, I03, I04 and I05 are all bent over and pressed down firmly to properly maintain the parts in fixed relation. The lugs IOI to I05 inclusive bear against the under face of the base 82, while the lugs 98 and 99 bear against the portions III of the grounding member It will be apparent that the shield I4 is eiIectively grounded to the housing 83 by means of the lugs 16, I22 and I23 which are pressed firmly into engagement with the portions 85 of 'thehousing. The housing is then positively grounded to the plate II 4 by contact of lugs 98 and with portions II1. Thus the shield, housing and ground plate are all positively grounded to the thimble or bushing II5. All of the current carrying portions of the switch assembly are thoroughly covered by the shield member 14 which is interposed between them and the variable resistance strip I06. The actuating portions of the switch, including the pivot pin 34, cam 45, pitman 80, spring GI and abutment member 63 are all insulated from the current carrying portions of the switch by means of the insulated switch arm 32 and insulated switch arm cover 44.

The shield I4 will be seen to perform a number of functions. It serves as a securing means for securing the switch assembly to the housing. It serves to provide a stop to limit rotation of the variable resistance contact arm by means of the stop member I! which is engaged by the extension II3 on the disc 56. It serves as a stop to limit movement of the switch arm in each direction by means of the legs I20 and I2 I. It further serves to limit the movement of the cam 45 by means of stops "I1 and I8. It is to be noted at this point that, by contact with these stops at either end or the limit of movement, the metal actuating portions of the switch assembly are also grounded.

An additional function of the shield plate is provided by the kick-off lugs 80 and Ill. The function of these lugs is shown in Figure 6. The operating cam 45 is swung from the dotted line position of Figure 6 in clockwise direction to cause the switch arm and the movable contact assembly 35 to move to the left out of engagement with the fixed contacts 22 and 23. As the parts move past the dead center in the clockwise direction, as seen in Figure 6, the force stored in spring SI thrusts against the abutment 53 and tends to move the switch arm assembly to the left.

Resisting this movement is the gripping action of the movable switch members 36 and 31 upon the fixed contact member. This resistance may be considerable if the contacts have become somewhat roughened or pitted in use by arcing.

The continued movement of the cam and pitman to the right or in the clockwise direction, with the movable contact still in engagement with the fixed contacts, will bring the side of the spring BI against the stop 80. This stop 80 will then act as a fulcrum and, in addition to the force of spring SI, the thrust to the right against the lower end of the pitman in Figure 6 by the cam' 45 will cause a movement of the upper end of the pitman to the left, which will positively break any connection between the movable and fixed contact members. When moving the switch arm in the opposite direction the kick-off lug BI will have a similar effect in positively initiating the movement of the switch arm in the clockwise direction. It will be understood that the parts are so proportioned and located that these kick-cit lugs will merely initiate the movement which will be completed by the force stored in the spring SI independently of the speed of movement of the actuating cam 45.

The movable and fixed contacts shown in detail in Figures 8 to 11, are specially designed to insure a firm, clean contact and to prevent arcing from occurring between the contacting surfaces. The upper member 38 is formed of heavier material and is substantially rigid. The lower menber 31 is formed of lighter spring material and is relatively flexible. The contact arm assembly is biased downwardly toward the supporting plate 20 by means 01' the thrust of the spring GI against the abutment member 63. The pivot portion of the arm is held spaced from the base 20 by means of the enlarged portion II of the pivot pin. The openings in the arm members fitting about the portion 69 of the pin have a somewhat loose fit so inner face of the base plate 26. The contact por-. tions 28 and 29 of the two fixed contacts are spaced upwardly from the inner face of the base 20 so that the downturned contact edges 40 and 4| slide under the fixed contact portions 28 and 29. This is clearly shown in Figure 9.

The contact portions 36 and 31 spring apart sufficiently to grip the fixed contact portions 28 and 29 firmly between them. The major portion of the spring action is afforded by the lighter, more resilient lower contact member 31. The contact edges 30 and 3! of the fixed contact portions 28 and 29 are formed upon an angle to the contacting edges 40 and 42 and 4| and 43 of the movable contact member. I'hus it will be seen fromv an examination of Figure 10 that the normal point of contact between the fixed andmovable contacts will be adjacent the free end of the movable contacts and adjacent the inner end of the fixed contact edge.

Also as shown in Figure 11, due to the downward bias given the movable contact members, the initial contact between the movable and fixed contacts will be between the heavier movable con-- tact member 36 and the fixed contact 29. This will cause any initial arcing to take place between the heavier movable contact and the comparatively heavy fixed contact. If, through repeated operation, the point of initial contact between the movable contact and the fixed contact is worn away, the point of initial contact will progress down the sloping fixed contact edges 30 and 3| toward their outer ends.

The arcing on opening or closing the switch occurs on surfaces which are not normally in contact when the switch is closed. This will be apparent from Figures 9 and 11, which show that the initial and final contacts which may are are on the upturned lip 43 of the movable contact. When the switch is in closed position this upturned lip is not in engagement with the fixed contact member 29. Consequently, any arcing or pitting or fouling due to arcing which may occur will not affect the surfaces in contact when the switch is closed and carrying the current. It will also be apparent that the spring action of the two movable contact members and their separation by the fixed contact members, causes a wiping action over the final contact surfaces which will keep these surfaces clean and free from oxide or foreign matter. The switch consequently will have a low resistance even after extended use.

By blanking my housing member from the strip sheet metal as shown in Figure 16, I am enabled to use usual types of commercial sheet steel and have the housings uniformly and accurately positioned relative to the fixed base of the resistance unit. As has been stated above, the diametrically opposite lugs i114 and H15 are the ones which are used to positively locate the housing relative to the base, the remaining lugs somewhat loosely fitting in their associated notches. The blank is stamped from the strip sheet metal in such a manner that the opposite lugs 14 and I I15 are aligned along the line of grain or fibre of the metal.

It will be understood that sheet metal of commercial types has a grain or fibre running lengthwise of the sheet metal, this grain or fibre being produced by the normal rolling operations used in forming the sheet metal. It has been found that. due to this grain and also to some extent due to variations in the internal structure of the sheet metal when produced commercially, there is considerable drift in the lugs blanked out during the lugs for the actual location I can assure that these lugs will be drawn substantially without relative drift between them if they are blanked out from the sheet metal on'opposite ends of a diameter of the blank aligned along the line of grain or fibre of the metal. This enables the forming of a cover which will be accurately positioned on the base and which may be cut from commercial types of sheet metal. This results in a very considerable saving in expense in the forming of these blanks. While metal may be secured without substantial grain, it is more expensive than usual types of metal and also diflicult to secure it with absolute uniformity of structure.

The grounding plate H4 is an important feature of the entire combination shown. This plate has a double function in serving as a grounding connection and also by means of the ears H6 serving as a locating device for locating and preventing rotation of the unit after it is assembled on a chassis. It will be understood that positive means preventing rotation of the unit is important in addition to the clamping action of the securing nut I25. This is for the reason that it may take considerable torque to operate the switch, and also since the rotation of the shaft is stopped by a positive abutment in the housing there is a tendency to gradually rotate the assembly unless it is positively locked against rotation relative to its support.

Another important feature of the grounding plate H4 is that the portions which overlie the resistance strip I06 are relatively small and are also bent away from the base 82 so as to minimize any capacity effect between the resistance strip and grounding plate. This has a desirable effect when these units are used in highly sensitive circuits for which they are adapted.-

It will be noted that the various ears on the lower edge of the housing member 83 are all shown with a relatively wider portion adjacent the body of the housing, which wider portion fits in the notches in the base member 82. This wider portion is of substantially the same extent as the thickness of the base 82. This makes it simple and easy to bend over the reduced portions of the lugs against the outer face of the base plate without any distortion of the body portion of the lug or tendency to spring it outwardly as the end is bent over.

While I have shown certain preferred embodiments of my invention, these are to be understood as illustrative only, as it is capable of change and variation to'meet difieringconditions and requirements and I contemplate such changes and modifications as come within the spirit and scope of the appended claims.

I claim:

1. In a switch assembly, a {non-conducting base, a snap switch supported by the base, a metallic shield adjacent to the switch, integral legs on the shield engaging the base and maintaining the shield spaced therefrom, and members extending from the shield into the path of movement or switch parts to be engaged by said parts to assist in switch movement.

2. In a switch assembly, a non-conducting base, a snap switch supported by the base, a metallic shield adjacent to the switch, integral legs on the shield engaging the base and maintaining the shield spaced therefrom, and a plurality of members extending from the shield into the path of movement of switch parts to be engaged by said parts during switch operation, certain of said members assisting in switch movement and other of said parts serving as limiting stops for switch movement.

3. In a switch assembly, a non-conducting base, a snap switch supported by the base, a metallic shield adjacent to the switch, and a plurality of members extending from the shield into the path of movement of switch parts to be engaged by said parts during switch operation, certain of said members assisting in switch move ment and other of said parts serving as limiting stops for switch movement.

4. In combination, a tubular metallic housing, non-conducting end members for said housing, a switch secured to one end member, the other end member providing a thin plate-like base, a variable resistance carried against the inner face of said base, common actuating means for the switch and variable resistance, a metallic shield between the switch and variable resistance, said shield being secured to the metallic housing, a conductive grounding plate secured to the outer face of the thin base carrying the variable resistance, and an electrical connection between the housing and said grounding plate, the portion of the grounding plate overlying the resistance being spaced from the thin base to reduce capacity coupling between the resistance and the grounding plate.

5. In a variable resistance device, a thin fiat non-conducting base, an arcuate resistance strip carried against the inner face of the base, rotatable contact means carried by the base, a metallic housing enclosing the resistance, a conductive grounding plate carried against the outer face of the base, and an electrical connection between the housing and grounding plate, a portion of the grounding plate overlying the resistance, said portion being spaced outwardly from the base to reduce capacity coupling between the resistance strip and the grounding plate.

6. In a switch assembly, the combination of, a substantially flat non-conducting base, a snap switch mounted on said base, a metal casing for the switch, said casing having a substantially cylindrical metal side wall encircling the base, a part turned in from the edge of the side wall and overlying the outer face of the base to support the same against outward displacement with respect to the side wall, a plurality of metal tongues having reduced end portions forming shoulders and tangs, said base having apertures through which the tangs pass so that the shoulders on said tongues bear against the inner face of the base, the outer ends of the tangs being bent over the part turned in from the edge of the-casing side wall so that the base is confined between said part and the shoulders on the tongues, and a metal plate carried by the tongues and overlying the switch parts inside said casing,

7. In a switch assembly, a metallic casing having an open end and an inwardly directed abutment integral with the side wall of the casing at said open end, said abutment having an aperture therethrough, an insulating base in the easing supported by said abutment against outward displacement with respect thereto, said base having an aperture in alignment with the aperture of the abutment, switch parts mounted on said base, a tongue having a reduced end portion providing a tang and a shoulder, the tang projecting through the aligned apertures of the base and abutment and being clinched over the abutment to confine the base between the abutment and said shoulder and electrically connect the tongue with the casing, and a metal shield integral with the tongue and overlying the switch parts inside said casing.

8. In a combined rheostat and snap switch for use in radio circuits, a single substantially cylindrical metal shell, one end of which contains the rheostat, and the other end of which contains the snap switch, a non-conducting base having the snap switch mounted thereon and closing one end of the shell, and a shield between the snap switch and the rheostat comprising, a transverse metal wall having an integral side wall portion connected to said base and contacting part of the shell so that the shield and shell are electrically connected and the transverse wall isheld in position dividing the shell into a switch compartment and a rheostat compartment, and said transverse wall having an opening through which the actuating mechanism of the snap switch is rendered accessible for actuation by a. part moving with the movable element of the rheostat.

9. In an electrical control of the character described, a substantially cylindrical metal shell, a substantially flat non-conducting base, a. snap switch mounted on the inner face of the base, a transverse metal wall overlying the switch and having an integral side wall portion spanning the distance between it and the base, interengaging means on the side wall portion and the base for holding said transverse wall against rotation with respect to the base, said transverse wall being of such size as to fit inside the metal shell with its side wall portion closely adjacent thereto, means on the metal shell engaging over the base to confine the connected base and transverse wall between it and a portion oi! the metal shell with the base closing one end of the shell and the transverse wall electrically connected to the shell, said transverse wall having an opening therethrough, a metal actuating cam connected with the snap switch and having a part projecting through said opening, stop means integral with the transverse wall engageable by the metal actuating cam for limiting motion thereof and for grounding the metal actuating cam to the transverse wall and shell, said cam substantially covering the opening to coact with the transverse wall in shielding the switch from the space in the shell beyond the transverse wall, a manually operable control instrumentality in said space, and a driving connection between said instrumentality and the cam part projecting through the opening.

NEWTON C. SCHELLENGER. 

